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DoubleEndedQueue.java
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DoubleEndedQueue.java
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class DoubleEndedQueue<T>{
private static class Node<T>{
T data;
Node next;
Node prev;
}
private Node<T> top;
private Node<T> bottom;
public void enqueue(T data){
Node<T> node = new Node();
node.data = data;
if(top==null){
top = node;
return;
}
if(bottom==null){
bottom=node;
top.next=bottom;
bottom.prev=top;
return;
}
bottom.next = node;
node.prev=bottom;
bottom = node;
}
public T dequeue(){
if(top!=null){
T data = top.data;
top = top.next;
if(top!=null){
top.prev = null;
}
return data;
}
//maybe throw Null pointer exception
return null;
}
public T pop(){
if(bottom!=null){
T data = bottom.data;
bottom = bottom.prev;
if(bottom!=null){
bottom.next = null;
}
return data;
}
return null;
}
public T peekTop(){
if(top!=null){
T data = top.data;
return data;
}
return null;
}
public T peekBottom(){
if(bottom!=null){
T data = bottom.data;
return data;
}
return null;
}
}